Apparatus for controlling heating systems



Jan. 6, 1942. J@ T. EWANDOWSKI. 2,268,711

APPARATUS FOR CONTROLLNG HEATING SYSTEMS Filed Aug. 27, 1958 Patented Jan. 6, 1942 i UNITED STATES PATENT@- oFFlcE APPARATUS FOR CONTROLLING HEATING SYSTEMS `l"oseph T. Lewandowski, Chicago, Ill., assignor to Minneapolis-'Honeywell Regulator Company, Minneapolis, Minn., a corporation of'Delaware Application August 27, 1938, Serial No. 227,17?.

(Cl. y2364) 14 Claims.

My invention relates to automatic control Iof heating systems and is moreparticularly directed to the control of steamheating systems including the so-called steam, vapor, and vacuum types. Heretofore satisfactory control of steam heat-v fluctuations in water level, surging, and boiler currents will frequently cause a response by such an element when there is not a corresponding each demand for heating.

proportional vapor pressure in the system necessary for proper heating at all points.

In my system I overcome these difficulties by utilizing a pressure responsive device to stop the burner, thereby insuring that-once the burner to various types of heating systems, not being limited to any particular type of construction or form of fuel or burner apparatus. It is my purpose to secure protection by Letters Patent on all the various novel features, phases, and aspects of my inventionas set forth in the appended claims.

Among the objects of my inventionare:

To provide an efficient and reliable automatic control` system and method for heating systems employing a vaporizable heating medium.

'I 'o provide a control system forl heating systems employing vaporizableI heating medium which will insure thatk all parts'of the systemare properly supplied with heating medium upon T9 provide an automatic lheating systems employing a vaporizable heating medium in which heating is initiated in response to a device measuring the loadL upon the system and in which-heating cannot be terminated before pressure within the system has f Y reached a predetermined value.

has been started a satisfactory pressure necessary to cause all parts of the system to be adequately supplied with heating medium will bey attained before the burner is stopped.

On the other hand, a pressureresponsive device, particularly in vacuum systems cannot be satisfactorily relied upon for starting the burner. For instance, when a vacuum responsive device is arranged to start the burner upon attainment of a predetermined vacuum in the system, operation is not satisfactory because any number of factors may intervene to break the vacuum pre- 'venting its reaching the. necessaryvalue. For example, leaks inthe system or opening of the system for inspection or repairswill destroy the vacuum and :preclude proper starting of the burner. Therefore in my combination I employ 'a temperature responsive device for starting the burner which will do so whether or not a `pre determined vacuum has been established i'n the system. My system-therefore, provides for positive control, starting the burner immediately upon a need for heatingand maintaining it in operation until after assurance that a condition has been'reached whereby heat has been adequately delivered .to all parts of the system.

My system vhas various other important aspects and features'which will become apparent from the .detailed specification following. Itis to be understood that my invention is applicable -ping the stoker but which .cannot stop the stoker To provide an automatic control system for heating systems employing a vaporizable heating medium wherein heating is initiated in re'- sponse to temperature\and continued under control of a pressure controller which may stopand restart the system ifthe temperature is such as to indicate the need for further heating.

To provide a steam heating system having a firing de vice started by a return line temperature controller and maintained in operation by' a pressure responsive device.

To providea stoker firedl steam heating system' in which the stoker is started by a temperature controller and may be stopped by a pressure controller and -which has an automatic device for starting and stopping the stoker to keep the iire in the furnace from going out.

To provide a stoker red steam heatingfsystem having a control system including a temperature controller for starting the stoker and a pressure controller for stopping the stoker and an automatic device for starting and stopii it was started by-the temperature controller. -To provide anl improved control system for vheating systems, in which vheatingis initiated as compensated by outdoor temperature and is a predetermined` condi.v

in response to temperaturefof heating medium continued at least until tion of the heating medium is attained.

To provide an improved^control system for heating .systems employingyaporizable heating control system for independently ofthe temperature controller.

'To provide a stoker red heating system in which heating is initiated in response to tem- .perature of -heating medium as compensated by outdoor temperature, heating being then controlled in'response to pressure of heating medium and the system having an automatic device for starting and stopping the stoker when outdoor temperatures are such that heating is not required.

To provide an improved method of control of heating systems employing a vaporizable heat-L ingl medium. l

Referring to the drawing:

.Figure 1 represents my control system applied to a stoker fired steam heating system,

Figure 2 is a detail plan view of a portion of the control apparatus, and

Figure 3 is a sectional detail view of another portion of the control apparatus.

I have chosen to describe in detail as an illustrative embodiment of my invention a one-pipe steam heating system as shown in Figure l, embodying my improved control arrangement.

Numeral I designates a furnace orboiler forming part of a steam heating system for a building structure, a portion ofwhich is shown at 2. Connected'to the boiler I is a riser or supply pipe 3 which has branch pipes connected thereto, two of which are shown at 4 and 5 and to. which are connected radiators as indicated at 6 and 1 nated II which connects to the lower part of the spring 28, the lever I8 is rotated in a clockwise direction sufcientlyto open the switch I9.

In controlling my system I employ for primary control a thermostat responsive to the temperature of the return line II which temperature is a measure of the amount of heat beingused for heating the building; As the heating load upon a building increases, more steam will be required in the various radiators for heating and consequently the temperature of the condensate in the return line will rise. Therefore, I use an outdoor temperature responsive thermostat for compensating the control point of the return line thermostatic responsive mechanism so as to raise its control point as the outdoor temperature falls. Thus as the outdoor temperature goes down indicating a greater heating load, I supply more steam to the system as determined by the raised control point of the return line thermostat. The thermostatic control mechanism which I employ is of the electrical proportioning type and is generally designated at 23. The

'proportioning mechanism 23 comprises a Nbalgized the armature 26 assumes 'a positionas l. shown wherein this switch arm 21 does not engage either of the contacts 28 or 29. When the v energization of coil 25 preponderates over that of coil 24, the switch arm 21 engages contact 29 and when the energization of coil 24 preponderetes the switch arm 21 engages the contact 28. Primarily controlling the balanced relay is a controller generally designated at 30 comprising an expansible bellows 3I connected by a capillary tube 32 tof.- a thermostatic bulb -33 arranged adjacent to the return line II of the heating system. The bulb 33, the capillary tube 32, and belv lows 3I- are filled with a temperature responsive boiler. From the aboveit will be apparent that the present systenris of the type commonly designated as a one pipe System. It is to be understood however that the present disclosure is exemplary only and theinvention is equally applicable to other types of systems.

The furnace or boiler I is fired by an automatic stoker I3 which iselectrically driven, the motor for driving this stoker having electrical terminals I4 and I5. My invention is particu-l larly well adapted for systems employing a Stoker for supplying fuel in solid form .to the furnace but other forms of fuel supplying devices or A boilers may be utilized. p Associated with the boiler so as to be responsive to the pressure therein is a pressure actuated switch generally designated at` I6. The

- pressure responsive switch I 6 comprises an expansible bellows I1 responsive to the Pressure.

within the boiler and which acts upon a pivoted lever I8 carrying a mercuryswitch I9. The lever I8 is biased in closing direction of the mercury medium, which upon expansion or contraction.

controller similar to the controller 30 and comprising a thermostatic device having an expansible bellows 43 connected to an outdoor temperature responsive bulb 44 by a capillary tube 45. Bellows 43 is actuated in response to outdoor temperature in a manner similar to that in which bellows 3| is actuated in response to return line temperature. The bellows 43 actuates a pivoted lever 46 having an angular arm 41 which forms aslider cooperating with a slide wire re-.. sistance 48. The lever 46 is biased in a counter-- clockwise direction by a coil spring 49 which may be made adjustable the same as the coil spring 31. The two coils 24 and4 25 of the balanced relay are connected in series and the slide wire Aseries connected coils 24 and 25 by wires 5I and 52 in series with which are interposed the protective resistances 5'3 and 54. The slide wire 48 of controller 42 is connected in parallel with the slide Wire resistance 38 and the series connected coils 24 and 25 by wires 55 and 56 which connect the ends of slide wire 48 to wires 5| .and 52, respectively. c The mid point of the resistance 39 is connecte to the juncture of coils 24 and 25 by a wire58 and the slider 41 is connected to wire 58 .by a wire 59, the latter wire having a compensating resistance 60 interposed in series therewith. The

'balanced relay may controlvarious types of energized and disengage from their'associated contacts when neither of them are energized or when they are both energized. `Power for the mechanism designated at'V 23 is supplied bya voltage step-down transformer generally designated at and comprising a primary winding 1| which may be connectedl to a suitable source of external power (not shown) and a secondary winding 12. One end of the secondary winding 12 is connected to one end of the coil 24 by a wire 13 and the other end of secondary 12 is connectedto one end of the coil 25 by a wire 14, a portion of wire 15, and wire 52. The wire 15 connects to the fixed contact 29 and the fixed contact 28 is connected by a wire 16 to one end of coil 63. Opposite ends of the coils 62 and 63 are connected by a wire 11 and one end of coil 63 is connected to the juncture of wire 13 and coil 24 by wire 18. The other -end of coil 62 is connected to switch arm 21 by a wire 19 which has a branch wire 80 connected to switch arm 64. The fixed contact 66 is connected to the juncture of the coil 25 and wire 52 by a wire 8|.

I will describe the operation of the tempera-y ture responsive mechanism 23 in controlling the switch 65 in the description of operation following. The switch 65 as will later appearis arranged to control an electrical relay indicated generally at 83 and which relay in turn controls the stoker I3. The relay 83 comprises a coil winding 84 cooperating with an armature arranged to operate switch arms 85 and 86 cooperating with fixed electrical contacts 81 and 88, respectively. The armature of relay 83 also actuates a pivoted lever arm 89 to which is secured by riveting or the like, a flexible metal blade 90. Numeral 9| designates an angular lever having the shape shown on the drawing and pivoted at 92. The lever 9| has a generally horizontal portion 93 having a. slidable weight 94 engaged thereon which biases the lever 9| in a clockwise direction about its pivotl Integrally formed on a portion of the lever 9| is a lug or finger 95 whichis engaged by the exible blade 90 when the rela'y 83 is energized causing arm4 pair of cams |04`4and |05 through a suitable gear train |03 so' as to cause them to rotate'through one revolution in an hour. The cams |04 and |05 are frictionally mounted on an axle or shaft which isdrivenby the gear train |03 and the cams may be rotated with respect to the shaft. I The cams |04 and |05 are rotated in a clockwise i direction and the contour of thecam |05 as may best be seen in Figure 1l wherein cam l|05 is shown shaded has two abrupt drop-offs'at |06, the drop-offs being spaced apart a small amount. Cam |05 has two similar drop-offs diametrically vopposed on the opposite side of the cam'. lThe cam |05 has a rise at |01 from a portion of smaller diameter to a portion of larger diameter and a similar rise diametrically opposed on'the opposite side of the cam. The cam |04 has an abrupt drop-off at |08 and a similar abrupt drop-off diametrically opposed on the opposite side of the cam. The cam 04 also has two diametrically opposed projecting portions |09 and 0 which form rises in the cam contour. It will be seen that the portions of the cam contour of cam |04 between the drop-offs and the projecting porvtions is of slightly smaller diameter than .the remaining portions of the cam contour. The

projecting portion ||0 vis integrally formed as ing it over this circular edge can be made part of the cam contour so that the cam `|04 will 'be entirely circular except for the abrupt vdrop-off 4land rise |09 diametrically opposed to the dropoff |08 and projection ||0.V In the cam |04 is an arcuate slot ||6 and a second arcuate slot ||1. Numeral ||8 designates a handle which is screwed onto a pin extending from the cam |05 through the arcuate slot ||8 and which engages cam |04. By loosening the handle ||8, cam |04 may be .rotated relatively to cam 05 and the cams may then be secured in their relative posi-- vtions by tightening `the handle H8. Numeral ||9 indicates a lug forming a pointer which is struck up' from the surface of cam |05 and the end of which is disposed within the arcuate slot ||1.

1 to 7, as seen on Figure 1, these figures designating minutes for a purpose which will presently become apparent. l

Numeral |20 designates upon which is mounted a cam follower |2| so as to rotate therewith. Numeral |22 (see Figure 2) is a similarly shaped cam follower mounted on the arbor |20 so that it may rotate thereon. The cam followers 2I and |22 are made of insulating material Aand the cam follower 2| follows the -contour of cam |04 while the cam follower |22 follows the contour of cam |05. Also carried by the arbor |20 and 'arranged to rotate there-f with. is a lever |23. It will be understood that the arbor |20 and all theapparatus comprising control of the relay 83 and consequently the stoker `I3. The timing mechanism comprises an electric timing motor having an armature |0| and a winding |02. 'I'he timing motor drives a.

the timing mechanism may be mounted on'a suitable panel board |24 and the lever |23 has a pin v|25 extending through an opening |24' in this panel board. The pin |25 is connected by The portion of the cam |04 adjacent to the arcuateslot ||1l isv graduated ingures from an arbor or spindle l a coil spring |26 to a pin |21 formed on the panel board and the coil spring continually biases the lever |23 and arbor |20 in a counter-'clockwise direction, causing the cam follower |2| to bear against the contour of cam |04. Encircling the arbor. |20 between the cam followers |2| and |22 is a coil spring |30 which is attached to the cam followers in a manner to urge the cam follower |22 in a counter-clockwise direction against the contour of cam |05. Numeral |3| indicates asmall latch member which is pivoted to the end of the lever |23 (see Figure 2) and which has a finger |32 which engages in a notch |33 in the end of the lever |23. Secured to the carn fol'- lower 22 is a contact strip |134 at the ends of which are fixed electrical contacts |35 and |36. The center part of the strip |34 is fastened to the cam follower |22 by a screw |31 to which an electrical wire is connected. Secured to the cam follower |2| by screws |38 and |39 are contact brackets |40 and I4l, respectively, the contact bracket |40 carrying an electrical contact |42 and the contact bracket |4| carrying an electrical contact |43.

It will be seen that the operating finger 91, previously described, is disposed adjacent to the latch member |3| with the parts in the position shown in Figure 1. The portion of^the latch member |3| adjacent to the finger 91 is more or less pointed and when the relay 83 is energized causing arm 89 and blade 90 to move to the left so as to engage lug 95 rotating lever 9| counter-clockwise the finger 91 will engage latch member |3| moving it slightly about its pivot and riding over its pointed end so that finger 91 engages the underside of the end of lever |23. 'With the parts in this latter position, the finger 91 prevents the ,lever |23 and consequently thearbor |20 from rotating in a counter-clockwise direction. Further description of this mechanism will be made in the general description of operation following.

Also driven by the armature |0| of the timing motor is a suitable gear train generally designated at |41 which drives a time dial indicated at |48. Forming part of the gear train |41 is a pinion gear |49 meshing with a larger gear |50 as may be seen on Figure 2, the -gear train being arranged to rotate the time dial |48 once in twenty-four hours. The gear 50 is secured to a hub |5| which in turn is rotatably mounted on a spindle or arbor |52 which may be carried by the panel board |24 previously referred to, the pinion |49 extending through an opening |53 in the panel board. The time dial |48 is secured to the hub |5| and is spaced from the gear |50 by ,a spacing member |54. Half of d/ial |48 is shaded Cas seen in Figure 1 and the shaded half is graduated in hours from 1 to 12 representing the hours from 12 a. rn. noon until l2 p. in. midnight. The other half of the time dial |48 is notshaded and the periphery of this half is graduated in hours from 1 to 12 designating the hours from 12 p. m. midnight to`12 a. m. noon. Rotatably mounted on the hub |5| are two half dials |55 and |56. The half dial |56 is shaded andits periphery is graduated in hours from 1 to 12 representing the afternoon part of the day, this half dial being utilized for setting the time of night, shut-downs as will as may be seen in Figure 1 through which the graduations on the half dial |55 are visible. Numeral |51 represents a ring having a pointer |58 integrally formed therewith, this ring being splined onto the hub |5| so that the pointer |58 may not be rotated relatively to the hub. The

half dials |55 and |56 and the ring |51 carryingf the pointer are secured in relative position with respect to the hub |5| by a thumb screw |59- engaging on the end of the hub. By loosening the thumb screw the relative positions of the half dials |55 and |56 may be adjusted relatively to each other and to the `time dial and by tightening the nut |59 these elements may be secured in the desired positions. A disc |60 is secured to the end, of the arbor |52 and interposed between this disc, encircling the arbor and abutting against the end of the hub |5| is a coil spring |6|. Thus by grasping the thumb nut |59, the arbor |5IA and all the elements secured thereto may be longitudinally reciprocated on the arbor |52 against the force of coil spring |6| so that gear |50 may be brought out of engagement with pinion |49 so-that the hub and the time dial |48 may be freely rotated. Arranged adjacent the periphery of the time dial |48 is a bracket |62 secured to the panel board |24. Etched upon the bracket |62 is an index marker |63 for purpose Vof setting the time dial |48. It will be understood that by grasping the thumb nut |49 and freeing the gear |50 from engagement with pinion gear |49, the time dial |48 may be adjusted so that the proper time of day on` the time dial may be set opposite the index |63. In other words, the graduations on the time dial |48 actually represent the time of day and if this dial should get out of synchronism by reason of failure of power for the timing motor or the like, it may be again reset to the proper time in the manner just described.

Numeral |65 designates a pivoted lever` pivoted at point |66 and having a shape generally as seen on Figure ,1. The lever |65 has an angular portion' |61 which forms a cam follower arranged to engage the perlpheries of the half dials |55 and |56 which form cams. The lever |65 is continually biased in a counter-clockwise direction by a coil spring |68 and the lever has a generally horizontal portion |69 carrying mercury switch |10. The hub |5| is arranged to rotate in a counter-clockwise direction and whenever the cam follower |61 rides off the periphery of the shaded-half dial, the coil spring |68 will rotate the lever |65.in a counterclockwise direction against a stop |1| causing opening of the mercury switch |10 which is normally closed whenever the cam follower |61 is following the periphery of lthe half dials. The mercury switch |10 forms a night shut-down switch for the system and vin the description of the operation following the manner of setting the night shutdown adjustment andy for restarting in the morning will be pointed out.

Numeral |13 is an electric time switch which maybe of an approved conventional type and which is adjustable so as to close the electric circuit therethrough at a predetermined time and to again open it after it has been closed for a predetermined duration of time.

resenting the hours inthe morning half of the l day, this half dial being utilized for adjusting the time at which the system is restarted after a night shut-down as will presently become apparent. The half dial |56 has an arcuate slot Power :at suitable voltage forv the relayA 83 is supplied from a step-down transformer generally designated at |14 and comprising a primary winding |16 which may be connected to a suitable source of external power (not shown) and a secondary winding -|11.

connects to the slider 36.

I Operation In my system with an outdoor 'temperature of 70, the return line temperature should be slib parts in the position shown,l these temperatures prevail and the sliders 35 and- 41 are in the mid( l control point of the controller 30 can be shifted positions of their associated resistances and therefore the coils 24 and 25 of the balanced relay are equally energized. Assuming for the moment that the controller 42 is not present, if the return line temperature falls bellows 3| will con-fv tract moving slider 35 to the left along slide wire resistance 38 and slider 36 to the right along slide wire resistance 39. It will be understood that the potentiometer formed by the controller 30 acts as a voltage divider for the voltage available between wires 13 and 14 for energizing the respective coils 24 and 25. In other words, as `s lider 35 moves to the left, the voltage drop between slider 35 and wire 52 is increased and therefore this increased voltage is impressed upon the coil 25 between the wire 52 and wire 58-which of slider 35 to the left decreases the voltage impressed upon the coil 24. When the,v voltage impressed on coil 25'preponderates a predetermined amount, armature 26 will move to the right moving switch farm 21 so as to engage fixed contact 29.

coil 62 which is as follows: from secondarywinding 12 through Wire 13wire 18, wire 11,coil 62,-

taining circuit for coil 62 is completed as follows:`

from secondary winding 62 through wire 13, wire 18, Wire 11, coil 62, wire 19, wire 80, switch Similarly, movement switch 21.

The fractional part'of the resistance 38 overwhich the slider 36 need move in order to actuate switch 21 can be selected automatically by the compensating controller` 42. In other-words, the

from one point on the resistance 38 to another by the controller 42. For example, should the outdoor temperature fall, it will indicate the need for a greater amount of heating and consequently that an increased amount of steambe supplied tothe system. Anincreased supply of steam will mean that the temperature of condensate in the return line will be higher. Therefore when the outdoor temperature falls, provision must be made for 'a higher return line temperature. Now as above described, the potentiometer formed by controller 42 is in parallel with controller 30. AS outdoor temperature falls, slider 41 Will move to the left along slide wire resistance 48. This controller will act as' a second voltage divider tending to unbalance the 'energization of coils 24 and v25. As slider` 41 moves to the left, it will be seen that it will bring about closure of switches 64. and 65 and in order to rebaiance the cons 24 and :aine slider 35 of controller 38 will have to move to the right, that is, the temperature affecting bu1b- 33 will have to rise causing slider to move to the right to balance the leftward movement of sliderl 41 of This will Vcomplete an energizing circuit for i compensating controller 42. It will be seen that the eiect of this movement of the compensating cont'roller will be to move the control point of controller 30 to the right to a higher temperature point on slide wire resistance 36. It follows therefore that the outdoor bulb 44`measures the heating load andthe heat supply is adjusted acblade 64, wire 8|, wire 52, wire 15, and Wire 14 back`to secondary winding 12. By reason of this maintaining circuit, coil 62 remains energized independently of lthe original circuit through which it was energized. Assume now that .there is a rise in temperature of the return line causing slider 35 to'nove to a position slightly beyond its original position. Energization of coil 24 will not preponderate over that of coil 25 and armature 26 will be movedA to the left so that switch arm 21 engages fixed contact 28. 'An energizing circuit for neutralizing coil- 63 will nowcordingly by maintaining 'the corresponding necessary return line temperature.v

'lhe function of resistance 60 is to insure that controller 30 always dominates rather than controller 42. Resistance limits the effect of con` troller` 42 so that even if slider 41 is at one end or the other of resistance 48, controller 38 still operates to control relay 6| without slider 35 moving oil resistance 38.

he resistance 39 is known as a corrector resis ance and its purpose is to increase the amount yof resistance in the connection between the juncture of coils 24 and 25 and the slider 35 as the Vslider 35 moves in one direction or the other over resistance 38. The reason for the need of this corrector resistance is that as slider 35 moves to the left,'f or example, changing the voltage'drops between wires 5l and slider 35 and between slider.

12, wire 13, wire 18, coil 63, wire 16, fixed contact 28, switch blade 21, wire'19, Wire 88, switch blade 64, fixed contact 66, wire 8|, wire 52, wire 15, and

wire 14 back to secondary winding 12. As Asoon as neutralizing coil 63' is energized, it will neutralize the effect of coil 62 upon the armature -associated therewith and the switch arms 64 and 65 will disengage from their `associated contacts. Opening of switch 64 will interrupt the above described'circuits for both the coils 62 'and 63.- From the description so far, it willbe understood 35 and Wire 52, the rate of change of voltage drops acrossithe coils 24 and 25- changes at a greater rate. Therefore as sliders 35 and y36 move in one direction or the other, a part offre- V,sistance 39 is inserted in series, with wire 58 and that after coil 62 is once energized it does not become deenergized until' switch blade 21 engages contact 28. It will be seentherefore that.

the controller 30 has a fixed operating diieren when the elements are properly proportioned,

the rate of change of voltages across coils 24 and 25 is reducedv to the desired rate rate control is secured.

From the foregoing, it should now be obvious' that the switch 65 is closed at a predetermined closes is raised.: Mercury switch |9 is a normallyv closed switch and mercury switch |10 is normally closed during the daytime. With these mercury the resistance 38 to cause actuation of the whereby accuslider 35 need move over only a small fraction of 75 switches closed, when switch 65 closes, a circuit energizing the relay 83 is completed as follows: from switch blade 65 through wire |80, wire I8I,

` what position they are in at the time of deenerwire |82, Contact bracket |4I, contact |43, con' of relay 83, switch blades 85 and 86 engage their* associated contacts, the switch 86 completing an energizing circuit to the stoker I3 vas follows: wire |80, which leads to a suitable source of external source of power, switch blade 86, fixed contact 88, wire |8I, terminals I5 and I4 of the motor driving the stoker and wire |82 also leading to a suitable source of external power. Closure of switch 85 completes a maintaining circuit fcr the relay 83 which is controlled by switch I8 but which is independent of switch 65 and is as follows: from secondary winding |11 through wire |84, coil 84, wire |83, screw |31, contact strip 34, normally closed contacts |35 and |43, contact bracket |4I, wire |82, wire |8I, fixed contact 81, switch blade 65, wire |83, wire |88, mercury switch |10, wire |81, wire |86, mercury switch I8, and Wire |85 back to secondary winding |11. Thus it will be seen that when the tem perature responsive mechanism has energized thestoker, fuel will be continuously supplied to the furnace under the 'control of the pressure responsive switch I6 until suicient boiler pressure has been built up so as to cause interruption of the above described maintaining circuit. high enough boiler pressure will therefore be assured so that there will be no danger of radiators on`upper floors not receiving an adequate supply of steam upon a thermostatic demand for heatmg.

. en the relay 83 was energized, lever 8| was rotated in a counter-clockwise direction in a manner to latch the lever |23 in a raised positionl as already described in the structural part of the description. The cams |04 and |05rotate constantly but because of the lever |23 being so latched in its upper position the position of the contacting mechanism operated by the cam followers is not changed as long as the parts remain in the last described position. The temperature responsive mechanism may become satisiied now at any time causing the switch 65 to open but the structure will remain in operation until at a predetermined` boiler pressure the switch I6 is opened interrupting the above described maintaining circuit and deenergizing the relay 83. Switches 85 and4 86'will now open and arm 88 will move to the right about its pivot disengaging blade 80 from lug 85. However, lever 8| will not now be returned to its original Vposition under the influence of weight 84 tending to rotate it clockwise because the finger 81 is latched in a position to the left of the pointed end of latching member |3| with lever4 |23 in a raised position. Now the purpose of the timing mechanism is in part to operate the structure at short intervals .when 'there are no thermoand may be in any position. lRegardless of 75 gization of relay 83, as soon as either one of the projections |08 or ||.0 on cam |04 engage the cam follower I2| the arbor |20 will be rotated clockwise moving the lever |23 with it suiiiciently so that latching member |,3I will be raised out of engagement withfnger 81. Immediately upon this occurring, lever 8| will be rotated clockwise `under the influence of weight 84 and will assume a position as shown in Figure 1. Now as soon as the projection |08 or ||0 has passed the cam4 follower |2I, the latter cam follower will be riding on asurface of cam |04 of larger diameter. Arbor will now be free to be rotated in a counter-clockwise direction and therefore both the cam followers |2| and |22 will be free to drop into the drop-offs in the contours of their associated cams. Assuming now that for an appreciable time there are no thermostatic 'demands for heating. At a predetermined time after cam follower |2I has .ridden over projection |08, for

example, releasing lever |23, cam follower I2| will be in the position shown in Figure 1. Upon continued rotation now of the cams, cam follower |2| will drop into the drop-olf |08 permitting arbor |20 to rotate .slightly in a counter-clockwise direction. However, cam follower |22 will continue to follow the contour of cam |05 and will not rotatev with cam follower I2 I. Upon rotation of arbor |20 with cam follower I2 I, bracket |40 will bring contacts |42 and |36 into engage' )ment and bracket |4I will cause separation of contacts |43 and |35. Upbnclosure of contacts |42 and |36, an energizing circuit for relay 83 is completed as follows: from secondary |11 through" wire |84, coil 84; wire |83, screw, |31,

contact bracket |34, contacts |36 and |42, contact bracket |40, wire |86, 'mercury-switch I8,

wire |85 back to secondary winding I 11. Energization of relay 83 will cause closure of switches 85 and 86, closure of switch. 86 energizing the stoker motor through the circuit already described. Upon energizationof relay 83 this time, however, the lever 9| will not be 'permitted to be rotated in a counter-clockwise direction in the manner above described for the following reason: at the time that can follower |2| drops into the drop-off |08 of cam |04, as pointed out above,

` arbor |20 is rotated slightly in a counter-clockmoving the lug 85 to the left. A

Y The stoker is now in operation and will continu'e in operation for a predetermined. number of minutesuntil the cam follower |22 drops in the rst drop-off* |06 of cam I 05. This will happen at an adjustable period ranging from 1 to 7 minutes after cam followerl I2| dropped into drop-olf |08 starting the stoker. In dropping into the first drop-off |06, cam follower |22 will rotate slightly in a vcounterclockwise direction about the arbor |20 which does not rotate at this time (it will be recalled that coil spring |30 biases cam follower |22 about the arbor |20 in a counterclockwise direction against the contour of cam |05). When cam follower |22 drops into the first drop-oit |06 as described, the contact strip |34 carried thereby will be moved so as to Relay 83 will now be deenergized and switches 85 and 86 will open causing termination oi` opera tion of the stoker. It will be understood that cam follower |22 will remain in the first drop-off |06 for a very short time of only a few seconds and that during this time both the contacts |42 and |36 and the contacts |43 and |35 will be separated. The reason for this construction whereis substantially half of that of the twenty-four hour dial |48. In other words, it would take in both sets of contacts are separated for a brief |06 and rotating slightly further in a counterclockwise direction thereby moving the right end of contact strip |34 upwardly so as to bring contacts |35 and |43 into engagement. From the foregoing, it will be understood thatthe`stoker is energized in response to the timing mechanism for a period of time determined by the angular spacing between the drop-off |08 of cam |04 and the rst drop-ofi' |06 of cam |05.r The duration substantially twelve hours for the cam follower |61 to traverse the entire circular periphery of the shaded half dial from one extremity to the other. With the above described adjustments having been made, it will be seen in Figure 1 that the cam follower |61 is substantially opposite the figure 10 on the shaded half dial. Thus with the dials rotating counter-clockwise, it will be substantiallyten hours after the time of setting that the cam follower |61 will drop oif the shaded half dial. With settings being made at 10 a. m., it follows that at 8 p. m. cam follower |61 will ride off the edge of theshaded half dial and lever |65 will be rotated counter-clockwise so as to open the switch |10. When switch |10 is open the system may not be energized in response to the thermostatic mechanism inasmuch as the -above described circuit controlled by switch 65 Y passes through the mercury switch |10. Howof timed operation of the stoker can be adjusted Figure l, the angular spacing between drop-offs |08 and |06'is madesmallei` as the duration of timed stoking operation is correspondingly shortened. When this latter adjustment is made, it is seen that the graduations on the cam |04 adjacent the pointer IIS will bring a smaller number indicating a smaller number of minutes of timed stoker operation opposite tothe pointer. When it is desired to manually actuate the contacting mechanism, the cams can be rotated together on the arbor |20 by grasping the handle I8 and applying a torque thereto.

From the foregoing it will be apparent that when the stoker is energized in response to a thermostatic demand for heat the stoker will remain in operation until stopped by the pressure l .ing this adjustment at 10 a. m., if sohe grasps the thumb nut |59 and in the manner -described sets the 'gure 10 on the unshaded half of the timed dial |48 opposite the `(index |63. Of course, if the proper time of day on the-dial |48 is already opposite the index |63 this adjustment need not be'made. -/If this adjustment is made at some time in the afternoon, that is, between noon and midnight,'the proper hour on the shaded4v half ofthe time dial |48 is set opposite the index l63. The above adjustment having been made, the thumb nut |59 is loosened and the ever, opening of mercury switch |10 does not interfere with the timed operation of the stoker for purposes of maintaining a re within the furnace. Now if the half dials had been adjusted relative to each other so that they were coincidingly superimposed upon each other, it will be seen that substantially twelve hours would elapse after cam follower |61 rode off the shaded half dial before it would be again engaged by the half dials. With such a setting the mercury switch |10 would be again actuated, this time to "closed position twelve hours after the night shut-down A time which would make it 8 a. m.

However, inasmuch as figure 6 on the unshaded l half dial has been set oppbsite the pointer |58, it'

isseen that the unshaded half dial is spaced substantially two hours -in a counter-clockwise direction from the shaded half dial. Therefore with the dials .rotating in a counter-clockwise direction after the cam follower |61 rides off the shaded half dial it will be substantially ten hours until the unshaded half idial engages the cam follower and repositions the lever. |65 in to closed position of the switch |10. Nightl shut-down having occurred at 8 p. m; when cam follower |61 rode oi the shaded half dial, ten hours later will make the time of closing of switch |10 6 a. m. the following morning.

The bracket |62 and cam follower |61 might take other relative positions with respect to the variousdials. The position of the pointer |58 is xed relative to the twenty-four hour dial |48 l 12 a. m. noon) were set opposite the index |63 l by rotating dial |48 two hours in4 a counterclockwise direction from the position shown, and suppose further that it were desired that night shut-down should occur twelve hours vleiter than this time of 172 a. m. noon. The shaded half dial would then be set with cam follower |61 subof dial |48 as seen on Figure 1.

stantially adjacent the gure l12 on the shaded half dial because it would be necessary for the cam follower to traverse the entire circular periphery of the shaded half dial which requires substantially twelve hours. Night shut-down would then occur at 12 p. m. midnight and therefore the pointer |58 would be pointing to the figure 12 on the shaded half dial (recalling that dial |48 and pointer |58 which movesv with it have been rotated two hours in acounter-clockwise direction from the position shown), and would correspondingly be pointing in the direction of the cam follower |61. The figure 12 on the unshaded half of dial |48 now being opposite the index |63, the figure 4 on the unshaded half of dial |48 would be adjacent the cam follower |61 and obviously it follows that the pointer |58 will be pointing at figure 4 on the unshaded half Thus it is seen that the pointer |58 has a definite proper position on the hub |5| depending upon the relative positions of the other elements of the apparatus.

The time switch |13 is adjusted so as to close the circuit therethrough at the same time in the morning that the mercury switch becomes closed. It will be seen that the time switch |13 closes the circuit controlled by switch 65, the latter switch being connected across the wires leading to the time switch and that therefore when mercury switch |10 closes in the morning at the same time the circuit normally controlled by switch 65 is closed irrespective of whether or not the thermostatic apparatus is calling for heat. The time of closing of the time switch |13 and mercury switch |10 in the morning marks the beginning fof a period commonly referred to in the art as morning pick-upl period. The time switch |13 maintains.the circuit therethrough closed for an adjustable period of time which may be of a duration of two hours, for. example, but can be adjusted by the janitor to be of a duration normally sufficient depending on the outside weather conditions to bring the temperature up to the normal daytime level after the night shut-down'. During the time that switch |13 is closed the structure is operated continuously or until it is shut down by the pressure switch I6. The circuit through time switch |13 remaining closed, it is seen that if the stoker is shut down by pressure switch I6` it may be control does not shift to the pressure switch but the timing apparatus can stop the firing apparatus after a predetermined period of operation. Thus the apparatus automatically and properly chooses whether or not control of the firing-de-l vice is to be shifted to the pressure switch responduring the time that time switch |13 is closed.

After time switch |13 opens the apparatus is, of course, again under the normal control of the thermostatic apparatus 23 and the automatic time mechanism provided for intermittent operation of the stoker.

From the foregoing it should be apparent to those skilled in the art that I have provided a highly novel and useful control system for'heating plants. My system provides positive control insuring that heat is adequately supplied to all parts of the system upon each demand for heating by the thermostatic -apparatus which apparatus is compensated so as to demand heat' in accordance with theload as determined by outdoor temperature. i f

The interlocking relation between my automatic timing and thermostatie control mechanism is unique in that when the firing apparatus is started in response to the thermostatic mechanism control shifts to the pressure switch but if the firing apparatus is started by the automatic timing mechanism for nre maintaining purposes sive to boiler pressure after the firing device has been started` By reason of my particular combination and operation thereof heating can be more uniformly and adequately controlled and in practice my system has been found to effect substantial economies in fuel consumption.

While--I have described in detail' the structure and operation of a preferred form of my invention, I desire that I be protected on all its novel features and aspects. Therefore I am to be limited not by my disclosure which is illustrative and exemplary but only as determined by the scope of the appended claims.

I claim as my invention:

1. In a heating system employing avaporizable heating medium, in combination, heating means including an electrically energizable device, control apparatus comprising means responsive to the temperature of the heating medium, means responsive to the pressure of the heating medium, an electrical relay controlling said device, said temperature responsive means controlling said relay Kto start said device and said control apparatus embodying means whereby upon starting of said device a maintaining circuit for said relay controlled by said pressure responsive means is established, automatic timing mechanism controlling said relay for operating said device at intervals to maintain a limited amount of heat in the heating means, said timing mechanism comprising thereby, said contacting means controlling said maintaining circuit, means operated by said relay rendering said contacting means inactuable to affect said relay when said relay is energized by said temperature responsive means whereby said timing mechanism will not interrupt said malntaining circuit, said means operated by said relay being ineffective to render said contacting means inactuable to affect said relaywhen said relay is energized by said timing mechanism.

' 2. In a heating system `employing a vaporizable heating medium, i-n combination, heating means including an electrically energizable device, control apparatus comprising means responsive to the temperature of the heating medium, means responsive -to the pressure of the heating medium, an electrical relay controlling said device, said temperature responsive means controlling said relay to start said device and said control apparatus embodying means whereby upon starting of said device a maintaining circuit for said relay controlled by saidpressure responsive means is established, automatic timing mechanism controlling said relay for operating said device at intervals to maintain a limited amount of heat in the heating means, said timing mechanism comprising contacting means actuable thereby, said contacting means controlling said maintaining circuit, means operated by said relay rendering said contacting means inactuable to affect said relay when said relay is energized by said temperature responsive means whereby said timing mechanism will not interrupt said maintaining circuit, said contacting means having a member cooperating with said relay operated means in such a manner that when said timing mechanism actuates said contacting means to energize said contacting means actuable relay said member prevents said relay operated l means from rendering said contacting means inv actuable to aiect said relay.

3. In a heating system employing a vaporizable heating medium, in combination, heating means including an electricallyenergizable device, control apparatus comprising means responsive to the temperature of the heating medium, means responsive to the pressure of the heating medium, an electrical relay controlling'said device, said temperature responsive means controlling said relay to start said device and said control apparatus embodying means whereby upon starting of said device a maintaining circuit for said relay controlled by saidpressure responsive means is established, automatic timing mechanism controlling said relay for operating said device at intervals to maintain a limited amount of heat in the heating means, said timing mechanism comprising a cam and contacting means actuable thereby said contacting means controlling said maintaining circuit, means operated by said relay rendering said contacting means inactuable to affect said relay when said relay is energized by said temperature responsive means whereby said timing mechanism will not interrupt said maintaining circuit, said contacting meansr having a member cooperating` with said relay operated means in such a manner that when said cam actuates said contacting means to energize said relay said member prevents said relay operated means from rendering said contacting means inactuable to affect said relay, said timing mechanism including means for initiating operation of said device and for terminating operation of isaid device after a period of predetermined duraion.

4. In a heating system employing a vaporizable heating medium, in combination, heating means including an electrically energizable device adapted for cycling operation and means for circulating heatingrmediumfrom said heatingv means to spaces to be heated, means indicative ofthe temperature of heating medium returning .to said heating means for energizing said device to initiate an loperating cycle ofsaid system, means responsive to a pressure condition of said medium indicative of circulation thereof substantially throughout the system, control means whereby after said device is energized by said temperature indicative means, it remains energized until a predetermined pressure condition is sensed b y said pressure responsive means, said device being then deenergized terminating the cycle, timing means for continuously energizing said device for a period of time unless said pressure responsive means is satised, said device being energized during said period of time if saidcondition responsive means is indicating a need for further heat, and' timing means for periodically energizingsaid devicev for `relatively short intervals.

5. In a heating systemv employing a vaporizable heating medium, in combination, heating means including an electrically energizable device, control apparatus comprising means responsive to the temperature of the heating medium, means responsive to the pressure `of the heating medium, anvelectrical relayl controlling said device, said temperature responsive means controlling saidrelay to startV said device, control apparatus embodyingv means whereby after starting of said device'it is maintained in operation under control of said pressure responsive means, said last means having a Vpreadjusted pressure setting at which pressure operation oi v l sive means is satised, and timing means for periodically energizing said device for intervals'of relatively short duration.

6. In a heating system employing al vaporizable heating medium, in combination, heating means including an electrically energizable device, control apparatus Acomprising means responsive to the Atemperature of the heating medium, means responsive to the pressure of the heating medium, and an electrical relay controlling said device, said temperature responsive means controlling said relay to start said device and said control apparatus embodying means whereby upon starting of said device a maintaining circuit for said relay controlled by said pressure responsive means established, and automatic means for intermittently energizing said relay and for-deenergizing said relay to operate said device for maintaining a limited amount of heat in said heating means, said automatic means including mechanism associated with the relay whereby the automatic means normally can control said maintaining circuit but not if the relay was energized by the temperature responsive means, so that the automatic means does not interrupt the maintaining circuit when the device has been Vstarted by the temperature responsive' means.

7. In a heating system employing a vaporizable heating medium, in combination, heating means including an electrically energizable device adapted for cycling operation and meansfor' circulating heating medium from said heating means to spaces to be heated, means indicative of the temperature of heating medium returning to said heating means for energizing said device to initiate an operating cycle of said system, means responsive to a pressure condition of.

said medium indicative of circulation thereof substantially throughout the system, control means whereby after said device is energized by said temperature indicative means, it remains energized until a predetermined pressure condition is sensed by said pressure responsive means,

said device being then deenergized terminating means including an electrically energizable'device, control apparatus comprising means responsive to the temperature of the heating medium,

means responsive to the pressure of the heating medium, and an electrical relay controlling said device, said temperature responsive means controlling said relay to start said device and said control apparatus embodying means whereby upon startingof said device a maintaining circuit for said relay controlled by said pressure responsive means is established, and automatic means' for intermittently energizing said relay and for deenergizing said relay operate said device for maintaining a limited amount of heat in said heating means, said automatic means norsponsive to the temperature of the medium returning to the heating means, means responsive to the pressure of the heating medium, an electrical lrelay controlling said device, said ternperature responsive means controlling said relay to start said device and said control apparatus embodying means whereby upon starting of said device a maintaining circuit for said relay is established whereby said relay remains energized irrespective of said temperature responsive means, said pressure responsive means controlling said relay and being operable to deenergize it at a predetermined pressure, said control apparatus including switching means for energizing said relay irrespective of said temperature responsive means unless deenergized by 4said pressure, responsive means, and timing means for intermittently energizing said device for predetermined intervals.

10. In a heating system employing a vaporizable heating medium, in combination, heating means including an electrically energizable device, control apparatus comprising means responsive to the temperature of ,the heating medium, means responsive to' the lpressure of the heating medium, an electrical relay controlling said device, said temperature responsive means controlling said relay to' start said device and said control apparatus embodying means whereby upon starting of said device a maintaining circuit for said relay controlled by said vpressure responsive means is established, automatic timing mechanism controlling said relay for operating said device at intervals 'to maintain a limited amount of heat in the heating means, said timing mechanism comprising contacting means actuatable thereby, said contacting means controlling said maintaining circuit to enable said timing mechanism to deenergize as well as to energize said relay.

11. In a heating system employing a Vaporizture responsive means is opened and said pressure responsive means being arranged to cause deenergization of said relay when the switch vof said pressure responsive means is opened.

12. In a heating system employing a Vaporizable heating medium, in combination, heating l means including an electrically energizabledevice,

control apparatus comprising means rresponsive to the temperature of the medium returning to the heating means, said temperature responsive means including a switch adapted to close'at a predetermined temperature, means responsive to the pressure of the heating medium comprising a switch adapted to be closed at a predetermined pressure, an electrical relay controlling said device, said relay comprising a main switch and an auxiliary switch. both of said switches' adapted to be closed when`the relay is energized and opened when the relay is deenergized, said temperature responsive means controlling a circuit for energizing said relay when the switch of said temperature responsive means is closed, said main switch of said relay controlling said electrically energizable device and said auxiliary switch controlling a maintaining circuit for said relay which is established upon energization of the relay to cause the relay to remain energized after having become energized even though the switch of said temperature responsive means is opened, said pressure responsive means being arranged to cause deenergization of said relay able heating medium, lin combination, heating means including an electrically energizable device, control apparatus comprising means responsive to the temperature of the medium returning to the heating means, said temperature responsive means including a switch adapted to close at a predetermined temperature, means responsive to the pressure of the heating medium comprising a switch adapted to be closed at a predetermined pressure, an electrical relay controlling said device. said relay comprising a main when the switch of said pressure responsive means is opened, and said control apparatus including timing meansfor intermittently energizing and deenergizing said device.

13. In a heating system employing a Vaporizable heating medium, in combination, heating means including an electrically energizable device, control apparatus comprising means responsive to the temperature of the medium returning to the heating means, said temperature responsive means including a switch adapted to close at a predetermined temperature, means responsive to the pressure of the heating medium comprising a switch adapted to be closed at a predetermined pressure, an electrical relay controlling said device, said relay comprising a main switch and an auxiliary switch, both of said switches adapted to be closed when the relay is energized and opened when the relay is deenergized, said temperature responsive means controlling a circuit for energizing said relay wherein the switch of said temperature responsive means is closed, said main switch of said relay'controlling said electrically energizable device and said auxiliary switch controlling a maintaining circuit for said relay which is established upon energization of the relay to cause the relay to remain energized after having become energized even though the switch of said temperature responsive means is opened, said pressure responsive means being arranged to cause deenergization of said relay when the switch of said pressure responsive means is opened, said control apparatus including timing means for intermittently energizing and deenergizing said device, and means for maintaining said relay energized irrespective of said temperature responsive means as long as the switch of said pressure responsive means is closed.

14. In a' heating system employing a vaporizn able heating medium, in combination, vheating means including an electrically energizable device, control apparatus comprising means responsive to the temperature of the heating medium atxa point remote from the heating means at which it\has g'lven up at least a part of its `heating effect. means responsive to the pressure of the heating medium, an electrical relay controlling said device, said temperature responsive means controlling said relay to start the device, control apparatus embodying means whereby after starting of said device it is maintained in operation under control of said pressure responsive means, said last means having 'a pre-#adjusted pressure setting at which pressure opera- 

